Proefschrift_vd_Beek

pathway for bacteria to enter the cochlea. Although histologic evidence did not support this pathway as part of the pathogenesis of meningitis, a precise explanation for the increased incidence of meningitis is still lacking. The withdrawal of the positioner from the market provided the clinical opportunity to study the influence of the positioner on speech perception. After the withdrawal, the implantation procedure in our clinic continued in the same manner, with the exception that the implantation was performed without insertion of a positioner. The electrode array implanted was the same for all patients and furthermore they encountered the same patient selection, implanting surgeon, fitting procedures, and rehabilitation. The positioner group (P-group) was implanted between July 2000 and July 2002. The 25 patients of this group were described earlier (Reference Note). The nonpositioner group (NP-group) was implanted between July 2002 and March 2003. This NP-group consisted of 20 patients. For both groups now, at least 1 yr of follow-up of speech perception scores is available. In this study, differences in speech perception found between the group with the perimodiolar electrode implanted as designed and the latter group are presented. Additionally, speech perception scores and the radial distances to the modiolus and the insertion depths, determined with MSCT (multislice computer tomography) for each electrode contact, will be correlated with perception thresholds and dynamic range. Finally, to obtain more insight into the effects of the positioner on intracochlear current pathways, electrical field imaging and modeling measurements (Vanpoucke et al., 2004) are discussed.

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TABLE 1. Patient demographics

P-group

NP-group

N

All 25

All 20

NPs (n 9)

NPd (n 11)

Age at implantation (yr) Duration of deafness (yr)

44.9 (13.4; 14.0–67.0) 18.5 (15.0; 0.2–43.0)

59.9 (10.8; 40.0–76.0)** 60.1 (7.6; 50.0–71.0)**

59.6 (13.3; 40.0–76.0)** 18.8 (14.4; 2.0–46.0)

16.8 (14.5; 0.3–46.0)

16.7 (16.5; 0.3–46.0)

Preoperative phoneme scores (%) Ipsilateral

6.3 (9.8; 0.0–33.0) 4.0 (9.8; 0.0–45.0)

7.2 (11.0; 0.0–42.0) 2.3 (5.9; 0.0–24.0)

2.0 (6.0; 0.0–18.0) 0.3 (1.0; 0.0–3.0)

11.5 (12.5; 0.0–42.0) 3.8 (7.7; 0.0–24.0)

Contralateral

Preoperative tone audiogram (%) Ipsilateral

111.6 (12.4; 85.0–130.0) 117.7 (12.0; 83.3–130.0) 119.6 (14.5; 83.3–130.0 104.2 (14.6; 85.0–130.0)

Contralateral

116.1 (7.8; 103.3–130.0)

109.6 (15.4; 85.0–130.0) 116.1 (14.5; 90.0–130.0) 116.1 (10.0; 101.7–130.0)

Data are averages with standard deviations of the population and minimal and maximal values between brackets. Significant differences, marked (**p 0.01), are between the P-group and the marked NP-group. Data are averages with standard deviations of the population and minimal and maximal values between brackets. Significant differences, marked (**p 0.01), are between the P-group and the marked NP-group.

MATERIALS AND METHODS All 45 patients in this study have been implanted in the Leiden University Medical Center with a Clarion CII HiFocus 1 cochlear implant. After having implanted the first 25 patients with a partially inserted positioner (P-group), the implantation of the next 20 patients was performed in our center in the same manner only without insertion of this positioner (NP-group). In the group with the positioner (P-group), this positioner was placed between the electrode array and the outer wall. The positioner was designed to have a slightly shallower insertion than the HiFocus electrode array. Furthermore, it was partially inserted with the insertion tool, resulting in a protrusion of the positioner from the cochleostomy of approximately 5 The positioner group (P-group) was implanted between July 2000 and July 2002. The 25 patients of this group were described earlier (Reference Note). The nonpositioner group (NP-group) was implanted between July 2002 and March 2003. This NP-group consisted of 20 patients. For both groups now, at least 1 yr of foll w-up of speech perception scores is available. In this study, differences in speech per- ception found between the group with the perimo- diolar electrode implanted as designed and the lat- ter group are presented. Additionally, speech perception scores and the radial distances to the modiolus and the insertion depths, determined with MSCT (multislice c mputer tomography) for each electrode contact, will be correlated with perception thresholds and dynamic range. Finally, to obtain more insight into the effects of the positioner on intracochlear current pathways, electrical field im- aging and modeling measurements (Vanpoucke et al., 2004) are discussed. the cochleostomy of approximately 5 mm. All pa- tients had a full insertion of the electrode array, except for one P-patient, deafened by meningitis. During implantation in this patient, a resistance was encountered and the four most basal contacts were not positioned inside the cochlea. The NP- group was limited to 20 patients because, after this group, the patients in our clinic were implanted with the new HiRes90K implant with HiFocus 1J elec- trode. After the operation of the ninth pati nt without a positioner, a trend of stagnation of growth in speech perceptio was detected t rough analysis of the initial results of the first six hooked-up NP-patients, with a maximum follow-up of only 2 mos. Addition- ally, the most basal electrode contacts in those six patients showed higher T-levels than the other con- tacts. Two factors were considered to be possible causes of these changes: decreased modiolar approx- imation and shallower insertion. Only the latter could be controlled in absence of the positioner, and it was decided to aim for a deeper insertion in the patients implanted afterward. The jog of the elec- trode was now placed inside the cochleostomy in- positioner. The electrode array implanted was the same for all patients and furthermore they encoun- tered the same patient selection, implanting sur- geon, fitting procedures, and rehabilitation.

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